Introduction:
Cardiovascular disorders are one of the leading causes of mortality in the world. As per WHO (World Health Organization) reports, cardiovascular disorders account for 30 % of all global deaths. Anemia in the blood is characterized by decreased hemoglobin levels (less than 13 g/dL in men and 12 g/dL in women). Anemia is commonly associated with chronic disease conditions. Studies have shown that anemia is an independent risk factor for cardiovascular complications.
How Does Anemia Result in Cardiovascular Complications?
The hemodynamic and clinical changes associated with acute anemia are reversible. But the changes related to chronic anemia lead to volume overload, which results in progressive cardiac enlargement and LVH (Left Ventricular Hypertrophy). Iron deficiency anemia can improve endothelial function and reduce cardiovascular disease outcomes.
The cardiovascular compensatory mechanisms that occur as a result of anemia include the following:
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Increased cardiac output.
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Vasodilation increases tissue perfusion.
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Tachycardia (increased heart rate).
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Arterial hypertrophy and remodeling.
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Arterial dilation.
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Formation of arteriovenous shunts.
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Hypoxic vasodilation as a result of hypoxic generated metabolites.
Anemia leads to eccentric left ventricular hypertrophy and stimulation of the renin-angiotensin-aldosterone system. Resting cardiac output increases when hemoglobin levels fall below 10 g/dL. Cardiovascular complications of anemia occur due to volume overload, worsening of the hyperdynamic state, cardiac dilation, and heart failure. Anemia also increases the morbidity and mortality associated with cardiovascular conditions.
What Is the Relation Between Anemia and Different Cardiovascular Conditions?
Heart Failure:
Congestive heart failure (CHF) is rare in anemic patients without underlying cardiac conditions. CHF occurs in cases of severe anemia, where the hemoglobin level is 5 g/dL or less.
Anemia worsens the prognosis in patients with heart failure due to hypoxia, the proinflammatory state, ventricular remodeling, and comorbidities like renal failure. Anemia is a marker of poor outcomes and a mediator of heart failure. Depending on the cause, the treatment for anemia includes folic acid, iron, erythropoiesis-stimulating agents (ESA), and blood transfusion.
Iron therapy improves anemia and cardiac function and increases oxidative stress. With increased hemoglobin levels, there is a risk of increased blood pressure due to changes in blood viscosity and reduced availability of nitric oxide. Therefore, blood transfusion is considered only in cases of severe anemia. Anemia in heart failure patients is normochromic (red blood cells have a normal red color) and normocytic (red blood cells have a normal size). Iron deficiency is common in acute cardiac failure and has a poor prognosis.
The main causes of anemia in cardiac patients are:
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Renal dysfunction.
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Activation of the inflammatory cascade.
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Increased renin-angiotensin-aldosterone activity.
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Hemodilution.
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Impaired erythropoietin production.
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Iron deficiency (absolute or functional).
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Folic acid deficiency.
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Vitamin B12 deficiency.
Hypertension:
Hypertensive individuals usually have normocytic anemia. Studies showed reduced hemoglobin levels in those with uncontrolled hypertension.
Anemic patients are found to have high nocturnal systolic blood pressure and a tendency for increased diastolic blood pressure. In hypertensive patients, anemia is associated with higher blood pressure values, a lower dipping status, and greater cardiovascular risk.
Arrhythmias:
Anemic patients showed electrocardiographic changes like QT interval prolongation, T wave inversion, ST segment depression, and reduced amplitude of the QRS complex. Anemia leads to reduced myocardial oxygen supply and hypoxia, which leads to a prolonged QT interval. A prolonged QT interval is a predictor of ventricular arrhythmia and cardiac death.
Coronary Heart Disease:
Anemia is one of the known risk factors for ischemic heart disease. Studies have shown that anemia negatively affects myocardial infarction patients. Factors related to red blood cells like hematocrit, hemoglobin, erythrocyte sedimentation rate, and RDW (red cell distribution width) are related to coronary heart disease. Anemia reduces the blood’s oxygen transport capacity, leading to a compensatory increase in heart rate, further reducing myocardial perfusion time.
Anemia is more prevalent in coronary heart patients who undergo hospitalization.
The main reason for anemia in such patients was:
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Kidney failure.
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Blood loss.
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Haemodilution.
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An inflammatory reaction that occurs in response to myocardial injury.
A small reduction in hemoglobin has a positive impact due to a reduction in blood viscosity, but a large fall in hemoglobin increases myocardial ischemia and worsens the prognosis. A person with anemia and a history of bleeding during admission should have restrictions on antithrombotic therapy, and a more conservative treatment approach should be used. Monitoring hemoglobin, hematocrit, red blood cell count, and RDW is important in patients with coronary heart disease.
Stroke:
Stroke is one of the leading causes of mortality and adult disability. The analysis of blood count abnormalities is used as a tool for evaluating the prognosis of stroke patients. A low hematocrit value points to hypoxia and cerebral ischemia. Ischemic and hemorrhagic strokes have increased mortality in cases associated with anemia. Higher stroke prevalence is seen in patients with increased hematocrit levels.
What Are the Cardiovascular Consequences of Hereditary Forms of Anemia?
Thalassemia:
Thalassemia is a common hereditary blood disorder due to decreased alpha or beta globin chain synthesis. The quality of life of the affected can be improved by transfusion therapy, but regular therapy increases iron deposition in the ventricular wall. This leads to pericarditis, valvulopathies, arrhythmias, and left ventricular dysfunction.
Sickle Cell Anemia:
Sickle cell anemia is characterized by sickle-shaped red blood cells and occurs due to hemoglobin S. The cardiovascular complications associated with sickle cell anemia are:
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Myocardial infarction (partial or complete blockage of blood flow to the heart).
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Cardiac enlargement.
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Acute stroke.
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Arrhythmia (abnormal heart rhythm).
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Chronic cerebral ischemia (impaired blood flow to the brain resulting in brain injury).
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Increased arterial stiffness.
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Microcirculation.
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Cardiac autonomic neuropathy (autonomic nerve fiber damage).
Hereditary Spherocytosis:
Hereditary spherocytosis is the most common genetic hemolytic anemia. The condition is characterized by spherical-shaped red blood cells on the peripheral blood smear. Severe anemia can occur due to virally induced bone marrow suppression, which may lead to heart failure.
Conclusion:
The treatment guidelines for managing patients with cardiovascular disorders and anemia should be updated to improve the prognosis. Factors related to red blood cells, like hemoglobin levels, hematocrit, RDW, and red blood cell count, should be evaluated in cardiac patients to determine the risk scores.
